Magnetic Fields Among Explanations Suggested

Why do whales and other marine mammals drift to shore and, thus, almost certain death? It is one of nature`s more mysterious questions, one that continues to baffle scientists today.

Much of the current research concentrates on the theory that strandings are the result of an animal`s navigational system going haywire. Scientists have looked at several reasons for that system breaking down.

``The one theory that is getting a lot of lip service now is that they use the Earth`s magnetic field to navigate . . . and so strandings occur where there are anomalies in magnetic fields,`` says James Mead, the Smithsonian Institution`s curator of marine mammals. ``It`s an awfully difficult statistical question, though. You have to compare where strandings occurred to magnetic anomalies.``

One researcher at Boston University tracked 70 mass strandings over the past 50 years and found many of them occurred near areas where there were irregularities in the geomagnetic topography.

Another possible reason for the breakdown of an animal`s navigational system is a problem with its hearing, scientists have speculated. Some beached dolphins, for example, have been found to have parasites in their ears, which may have caused hearing and navigational problems. But other researchers have found that all dolphins, stranded or not, have these parasites.

Dan Odell, a University of Miami marine biologist, has conducted research that suggests strandings might be related to branches of the Gulf Stream deviating from the main current and wandering closer to shore. Those branches may carry squid, and certain whales may follow the squid -- a primary food for them -- and end up too close to shore.

In the past, some people have speculated that strandings are actually intentional, that the animals are committing suicide. Odell is among those who dismiss this notion as ``too anthropomorphic.`` Instead, scientists prefer to investigate external, physical factors that may cause strandings.

One area that merits further attention, he says, is the role that pesticides and petroleum hydrocarbons (from oil spills) might play in strandings.

Like many other areas of scientific inquiry, however, lack of adequate funds often blocks such research. But members of the Stranding Network have taken tissue samples from beached animals and frozen them for later use, when money might become available.

``We all stockpile tissues,`` Odell says. ``It`s all by hook or by crook that you do all this.``